1. Field of the Invention
The present invention relates to a zoom lens which can be used as a photographing zoom lens of a compact camera.
2. Description of the Related Art
Among internal-zooming type zoom lenses of compact cameras in which a zooming operation is performed by moving one or more intermediate lens groups while maintaining the distance between the frontmost lens group and the rearmost lens group, zoom lenses in which the space between the frontmost lens group and the rearmost lens group is reduced immediately after the power of the camera is turned OFF are known in the art. In such conventional zoom lenses, the lens support ring which supports the rearmost lens group generally has a fundamental cylindrical shape and is provided with slots or cutout portions to guide the lens support ring itself or one or more lens groups positioned in the lens support ring in a direction, e.g., in the optical axis direction of the zoom lens.
Such a lens support ring has become the cause of difficultly in achieving a further reduction in size and weight of the photographing optical system of the zoom lens.
The present invention has been devised in view of the problem noted above, and accordingly, the present invention provides a zoom lens having a structure which can achieve a compact and light-weight zoom compact camera and facilitates the assembling of the photographing optical system of the zoom lens.
For example, a lens barrel is provided, including a first ring member having a ring frame portion and at least one leg portion which extends from the ring frame portion in an optical axis direction; and a second ring member, which is relatively movable in the optical axis direction with respect to the first ring member, the second ring member having at least one slot which extends in the optical axis direction, the leg portion being inserted into the slot so that the leg portion can move in the optical axis direction along the slot. The second ring member is coupled to the first ring member so that the second ring member is positioned substantially within a radial thickness of the leg portion.
It is desirable for a radially outer surface of the leg portion to be substantially flush with an outer peripheral surface of the second ring member.
It is desirable for a radially inner surface of the leg portion is substantially flush with an inner peripheral surface of the second ring member.
In another embodiment, a zoom lens is provided, having a frontmost movable lens group, at least one intermediate movable lens group and a rearmost movable lens group, in that order from the front of the zoom lens, the zoom lens including a lens support ring which supports the frontmost movable lens group; a linear guide ring positioned in the lens support ring to be movable along the optical axis; and a rearmost lens group support ring which supports the rearmost movable lens group, the rearmost lens group support ring being positioned in the lens support ring to move along the optical axis while varying a distance between the rearmost movable lens group support ring and the frontmost movable lens group. The rearmost lens group support ring includes at least one leg portion which extends parallel to the optical axis. The linear guide ring includes at least one slot which extends parallel to the optical axis, the leg portion being inserted into the slot so that the leg portion can move in the optical axis direction along the slot. The leg portion substantially fits within the thickness, in a radial direction, defined the slot of the linear guide ring with respect to a sectional plane parallel to the optical axis.
The leg portion can include an engaging portion which comes into contact with the lens support ring to prevent the lens support ring from moving along the optical axis relative to the rearmost lens group support ring to thereby maintain the distance between the frontmost movable lens group and the rearmost movable lens group.
It is desirable for a portion of the linear guide ring on which the slot is formed to be positioned in the lens support ring. The leg portion is inserted into the slot to be slidable in the optical axis direction so that the rearmost movable lens group is movable in the optical axis direction without rotating about the optical axis relative to the linear guide ring.
It is desirable for the linear guide ring to include at least one bridge portion which extends under a portion of the slot from inside of the linear guide ring. The bridge portion is in contact with the leg portion over a full width range thereof to prevent the leg portion from slipping into the inside of the linear guide ring.
It is desirable for the leg portion to include first support portions formed on opposite side edges of the leg portion, respectively, and for the linear guide ring to include second support portions formed on respective sides of the slot, wherein the first support portions are in sliding contact with the second support portions so as to prevent the leg portion from slipping into the inside of the linear guide ring.
The zoom lens can be a multi-stage-extension zoom lens barrel having a plurality of sub-barrels arranged concentrically about the optical axis, the distance between the frontmost movable lens group and the rearmost movable lens group being reduced when the plurality of sub-barrels are fully retracted.
The leg portion can include a resilient narrow portion extending parallel to the optical axis, a front end of the resilient narrow portion being formed integral with the leg portion so that a rear end of the resilient narrow portion serves as a free end. The engaging portion can be formed at the rear end of the resilient narrow portion and extends radially outwards.
It is desirable for each of the first support portions to include a tongue portion, and each of the second support portion to include a half groove portion on which the tongue portions is slidably positioned.
The zoom lens can further include a lens shutter unit positioned between the frontmost movable lens group and the rearmost movable lens group and around the intermediate movable lens group.
The present disclosure relates to subject matter contained in Japanese Patent Application No. 2001-206749 (filed on Jul. 6, 2001) which is expressly incorporated herein by reference in its entirety.